It has been known for some time that the light parameters of discharge lamps can be improved significantly by supplying them with energy in a pulsed form. These methods have attracted particular attention in the gating of high-pressure sodium vapor lamps, for raising the color temperature of the lamps from about 2,000.degree. K. to more than 3,000.degree. K. At the same time, an improvement in the color reproduction is possible. German Patents 2,657,824 and 2,825,532 disclose this technique.
When operating sodium vapor discharge lamps which contain several metal vapors and use bipolar pulses, demixing phenomena are to be avoided.
Then nature of the gating pulses, their shape, pulse width, duty cycle, rise and height have a decisive influence on the light parameters to be attained. Preferably, relatively broad pulses (about 100 to 200 .mu.s) and duty cycles of about 0.2 are generally used, the repetition frequencies being less than 500 Hz, as described in the German Patent 3,636,901.
At frequencies above 500 Hz, the discharge system tends to produce resonance phenomena, which become evident in the form of severe arc instabilities and light yield losses (German Patent 3,122,183). It is also known to change the pulse geometry and the pulse shaping in such a way, when using electronic stabilizers, that the pulses have a rapid transition from the cooling domain into the state of a specified pulse output, an extended reaction time at this level and a rapid return to the state of the cooling phase. For the pulse shaping, a multisectional delay line, network, consisting of capacitative and inductive components, has been suggested. As is known from investigations, the optimum pulse width for sodium vapor discharge lamps lies between 100 .mu.s and 200 .mu.s, so that an appropriate electronic stabilizer would be a very expensive and bulky component when delay lines are used for shaping pulses.
The, generation of relatively wide pulses of appropriate height places high demands on the stabilizer technology, requiring large amounts of energy to be stored and switched.